The continuous infusion of medicines, or discontinuous, controlled infusion such as that required, for example, when administering insulin, is generally carried out by means of so-called syringe pumps. Here the piston of a syringe is pushed forwards continuously or discontinuously by a suitable plunger and a medicine is administered to the patient via a hose connection and an injection cannula.
In patients with diabetes, the use of a pump for the application of insulin greatly facilitates the daily management of the disease. Here it is desirable that such an insulin pump be small in size and light weight. Precision, reliability and simple operation are generally assumed.
WO 01/72358 A1 discloses a drive device for a piston in a container containing an injectable product. This drive device contains a plurality of displacement stages and a drive for advancing the displacement stages, which drive acts on the displacement stages by means of spindle drives.
U.S. Pat. No. 6,723,072 B2 relates to a device for administering a liquid medicine with a piston arrangement which contains a shape memory element which is arranged between two segments and can alter its length. By alternately lengthening and shortening the shape memory element the piston arrangement is caused to perform a longitudinal movement since the two segments can essentially only be displaced in one direction.